why do third generation fermions interact more strongly with the higgs field than second, and second first. why does the top quark interact with the higgs field more strongly than an electron?

The couplings of the Higgs field are free parameters in the Standard Model and directly related to the masses of the quarks. Therefore, a quark with a larger mass will interact more strongly with the Higgs field. In effect, it is the interaction with the Higgs field that provides the mass, implying that a quark that interacts more strongly with the Higgs field will have a larger mass.

Yes, but this would be a rather strange situation where we would probably suspect that some symmetry was in play because there is no a priori reason for this to be the case.

In fact all the masses are almost zero compared to the top quark, so we could suspect a symmetry where all masses are null except the top quark, but this scenario is not asked/developed frequently, neither in literature nor even here in forums.

Given that the W bosons are the means by which quarks and charged leptons, at least, change from one flavor to another at frequencies that show a some crude relationship to the mass differences involved, surely the Higgs boson couplings and the CKM matrix that governs W boson quark flavor transformations, have some deeper connection to which we are not yet privy.

Also, it isn't obvious that it is possible for particles to be distinct from each other in some means other than their propensity to change from one type to another (which would have no observable consequences if all other properties were the same) if they do not have some different properties, so it stands to reason that given that they are identical in everything else, that they ought to have different masses, and are assignment of those masses to particular generations in order of mass is something that can be done without loss of generality in every case where there are distinct masses.

Also, it isn't obvious that it is possible for particles to be distinct from each other in some means other than their propensity to change from one type to another (which would have no observable consequences if all other properties were the same)

Pauli exclusion principle effects should be observable: in the "Higgsless Universe", electrons and muons would look the same, but you'd notice that sometimes you can cram two of them into the same state, and sometimes you can't.

Not if the Higgs coupling is the source of masses in the universe. If all the couplings were the same the Higgs boson and field would be much simpler mathematically.

in a higgless universe is it possible that there is NO difference between an electron tau or muon? they are all the same particle, the only difference is that sometimes the higgs is more strongly attracted to muon or tau, or that a muon or tau are quantized excited versions of electron

electrons and muons would look the same, but you'd notice that sometimes you can cram two of them into the same state, and sometimes you can't.

Not exactly. What would be observed is you can get 3 electrons into the same state. Eventually it would be explained as a hidden quantum number called "infracolor" or "ultracolor" or something like that, in analogy with QCD color.

Not exactly. What would be observed is you can get 3 electrons into the same state. Eventually it would be explained as a hidden quantum number called "infracolor" or "ultracolor" or something like that, in analogy with QCD color.

It is not gauge, so flavor is still a good name.

I wouldn't say "unphysical". "Trivial" and "unnecessary" seem to be more descriptive.

My vote is with "Trivial".

Is it right to think that while we need three different masses to have a full non trivial CKM matrix, we do not need six?

I am not sure that people would immediately conclude that. I suspect they would start putting together "ultraweak" theories to try and explain flavor. We sort of do this today with topcolor-style theories.

Is it right to think that while we need three different masses to have a full non trivial CKM matrix, we do not need six?

Has to be the right three. All the +2/3 or all the -1/3. That allows you to change the basis so the CKM matrix is the identity. If you make e.g. two of the +2/3's degenerate with one of the -1/3's, you still have a nontrivial matrix. However, that matrix will be real, so there will be no CP violation.